The specific control of gene activation and repression is vital for all aspects of eucaryotic cellular life, from differentiation to routine maintenance. The abrogation of these controls appears to be the basis of many diseases. In this proposal we will concentrate on studies on transcriptional mechanisms controlled by specific trans-acting factors. We have previously identified an element in the late promoter of a DNA virus, simian virus 40 (SV40), which responds to transactivation mediated by the early viral protein T antigen. Data suggest that T by cellular trans-acting factor (s) which are induced or activated by T antigen. It is also known that the presence of T antigen causes the activation of a anumber of cellulare genes. Presumably the induced or activated cellular factors activate cellular target promoters as well as the viral promoter. Thus a group of genes appears to be activated by a similar mechanism. We can exploit this situation for the characterization of this mechanism by isolating a set of cellular gene promoters which are activated under these conditions. Therefore, we propose to: l) isolate specific cellular genes which are activated in trans byu a mechnaism involving T antigen; 2) identify elements in the promoters of these genes along with the SV40 late promoter element, for structural similarities and , more importantly, functional similarity; 4) isolate and characterize the cellular trans-acting factor(s) involved in the activation of each promoter; and 5) isolate a set of activatable promoters and trans-acting factor(s). After isolation and characterization of a set of activatable promoters and trans-acting factors, we will begin detailed in vitro and in vivo studies to determine the normal functioning of these factors and promoters during the cell cycle and under different growth conditions. Additionally we propose to examine the chromatin structure of the activatable promoter elements as they convert form an inactive to an active state and vice versa. Such experiments will help to elucidate how the trans-acting factors mediate the gene expression control.